Sega made a number of announcements during their Sega Fes 2018 event, one of them being the reveal of the Sega Mega Drive Mini.
Sega revealed that the console will be released in Japan later this year to celebrate 30 years of the 16bit console.
— セガ公式アカウント (@SEGA_OFFICIAL) April 14, 2018
Currently not much else is known about the console, no price, hardware details, not even which games will be available to play on it (though you know Sonic the Hedgehog will be on there).
There are already small versions of Sega’s Mega Drive out there with built-in games, such as the Sega Genesis Flashback and the Sega Mega Drive Classic Console. Both were produced and released by AtGames, which relied on emulation and suffered a few issues. However, Sega’s Mega Drive Mini will be produced and released by Sega.
Also, Sega has re-released a lot of the games from the Mega Drive over the years, notably the Sega Mega Drive Ultimate Collection that was released on the PS3 and Xbox 360. Plus Sega will be releasing Sega Mega Drive Classics later this year in May for PS4 and Xbox One, with a lot of the same classic Mega Drive games.
Given that the original Sega Mega Drive was released in Japan in October 1988, Sega will likely time the release of the mini version for October 2018.
UPDATE 15/04/18 – AtGames revealed on Twitter that they would be developing the Mega Drive Mini, saying, “Sega is going to release the Mega Drive Mini in Japan, powered by the latest AtGames technology. This same new and improved technology will find its way into the US and other territories later this year!” They subsequently deleted the tweet.